Isocyanate-based rigid foam

ABSTRACT

An isocyanate-based rigid foam comprising the reaction product of an organic and/or modified organic polyisocyanate, a resin blend and, optionally, a relatively low molecular weight chain extender or crosslinker in the presence of a catalyst, and, optionally, further auxiliaries and/or additives, wherein the resin blend comprises a phthalic anhydride-initiated polyester polyol, a blowing agent comprising a C 4 -C 6  hydrocarbon, and a fatty acid or fatty alcohol ethoxylate compatibilizing agent. The blowing agent is soluble in the polyol composition, thereby reducing the risks associated with such blowing agents in processes for making rigid polymer foam articles and providing rigid foams having good dimensional stability and improved insulation properties.

This application claims benefit to provisional application Ser. No.60/074,120, filed Feb. 09, 1998.

FIELD OF THE INVENTION

The present invention relates generally to rigidpolyurethane/polyisocyanurate foam comprising the reaction product of anorganic polyisocyanurate and a stable polyester polyol compositioncomprising a phthalic anhydride-initiated polyester polyol, a C₄-C₆hydrocarbon blowing agent, and a compatibilizing agent having an HLB offrom about 7 to 12. The blowing agent is soluble in the polyolcomposition. The foam exhibits improved dimensional stability andthermal insulation properties including improved K factors.

BACKGROUND OF THE INVENTION

Hydrocarbons are gaining wider acceptance as viable alternative blowingagents in the manufacture of rigid polyurethane foams. Due to thenon-polar hydrophobic characteristic of hydrocarbons, they are onlypartially soluble, if not completely insoluble, in many polyols used tomanufacture rigid polyurethane foams. The insolubility or poor shelflife of hydrocarbon-polyol mixtures has, to date, limited the ability ofstoring batches of the mixtures for use at a later time. Due to the poorsolubility of hydrocarbons blowing agents in polyols, the blowing agentmust be added to the polyol composition under constant agitationimmediately before dispensing the foaming ingredients through a mixhead.The poor solubility of hydrocarbons also tends to lead to larger,coarser, or uneven cell structures in a resultant polyurethane foam. Asis well known, the thermal conductivity of a foam generally increaseswith a poor cell structure. Therefore, it is critical that hydrocarbonbe uniformly dispersed under constant agitation throughout the polyolmixture immediately prior to foaming in order to obtain a rigidpolyurethane foam having the desired thermal insulation values.

In U.S. Pat. No. 5,391,317, Smits sought to manufacture a foam havingboth good dimensional stability and thermal insulation usinghydrocarbons as blowing agents. This reference taught the use of aparticular mixture of C₅₋₆ alicyclic alkanes, isopentane and n-pentaneblowing agents in particular molar percents, in combination with apolyol mixture made up of an aromatic initiated polyether polyol, anaromatic polyester polyol, and a different amine-initiated polyetherpolyol. As the aromatic-initiated polyether polyol, Smits suggestedusing an alkylene oxide adduct of a phenolformaldehyde resin. Theparticular mixture of alicyclic and isomeric aliphatic alkane blowingagents is taught by Smits as producing a foam having good thermalinsulation values.

The problem of obtaining a closed cell rigid polyurethane foam havingboth good dimensional stability and thermal insulation at low densitieswas also discussed in “An Insight Into The Characteristics of aNucleation Catalyst I HCFC-Free Rigid Foam System” by Yoshimura et al.This publication reported the results of evaluations on a host ofcatalysts used in a standard polyurethane formulation to test theeffects of each catalyst on the thermal insulation and dimensionalstability of the foam. The standard formulation used contained 40 partsby weight of a sucrose-based polyether polyol, 30 parts by weight of anaromatic amine-initiated polyether polyol, and 30 parts by weight of analiphatic amine-initiated polyether polyol, in a 1:1 weight ratio ofaromatic to aliphatic amine-initiated polyols. This formulation wasselected based upon the findings that sucrose and aromatic amine-basedpolyether polyols exhibited poor solubilities with cyclopentane, whilealiphatic amine-based polyether polyols provided the best solubility forcyclopentane. As a result, 30 parts by weight of the aliphaticamine-initiated polyether polyol was used in the standard formulation.

Others have also tried to modify the polyol components in a polyolcomposition in an attempt to solubilize a hydrocarbon blowing agent inthe polyol composition. In U.S. Pat. 5,547,998 (White et al), the levelof aliphatic amine-initiated polyether polyols in a polyol compositionis limited to solubilize cyclopentane in the polyol composition. Whenreacted with an organic isocyanate, the polyol composition, comprisingan aromatic amineinitiated polyoxyalkylene polyether polyol and analiphatic amine-initiated polyoxyalkylene polyether polyol in an amountof 10 weight percent or less by weight of the polyol compositionproduces a dimensionally stable rigid closed cell polyurethane foamhaving good thermal insulation properties.

In U.S. Pat. 5,648,019 (White et al), the level of aromatic polyesterpolyols in a polyol composition is preferably limited to 18 weightpercent or less to improve the solubility of blowing agent in the polyolcomposition. The polyol composition is preferably reacted with anorganic isocyanate to produce a rigid closed cell foam having goodthermal insulation and dimensional stability.

Thus, it would be desirable to provide a polyester polyol compositionwhich has a hydrocarbon blowing agent solubilized therein which can beused to produce dimensionally stable rigid polyurethane foam having goodthermal insulation properties.

SUMMARY OF THE INVENTION

According to the present invention, a stable polyester polyolcomposition is provided comprising a phthalic anhydride-initiatedpolyester polyol, a C₄-C₆ hydrocarbon blowing agent, and acompatibilizing agent, wherein the blowing agent is soluble in thepolyol composition. The compatibilizing agent comprises an oxyethylatedfatty acid or fatty alcohol having an HLB of from about 7 to about 12,preferably from about 8 to about 11, most preferably about 10. In apreferred embodiment of the present invention, the compatibilizing agentis an oxyethylated fatty acid of the general formula R_(n)—COO(EO)_(x)H,wherein R_(n) is a C₁₄ to C₂₆ alkyl chain, EO represents an ethyleneoxide unit, and x is from about 5 to about 12. In one embodiment, thecompatibilizing agent comprises a C₁₈-C₂₀ fatty acid-initiatedoxyethylate having an average of about 8 ethylene oxide units permolecule. Preferably, the compatibilizing agent is present in an amountof from about 1.0 to about 25.0, more preferably 5.0 to about 15.0, mostpreferably 7.0 to about 10.0, parts by weight based on 100 parts byweight of the polyester polyol.

The blowing agents employed when used in association with the polyolcompositions of the present invention have been found to offer lowerdensities, improved K factors, improved thermal insulation propertiesand improved dimensional stabilities over foams produced using otherpolyol systems. The compatibilizing agent preferably facilitatessolubilizing the blowing agent in the polyol composition withoutsacrificing, and advantageously improving, the thermal insulation anddimensional stability of the resulting polyurethane foam. The blowingagent is preferably selected from the group of C₅ hydrocarbons,including isopentane, normal pentane, neopentane, cyclopentane andmixtures thereof. A preferred blowing agent mixture comprises a blend ofisopentane andlor normal pentane and cyclopentane. In another embodimentof the present invention, the blowing agent comprises a blend ofcyclopentane and isopentane, preferably in a weight ratio of about 70:30to about 40:60. The amount of blowing agent present in the polyolcomposition is preferably at least about 5.0 parts by weight based on100 parts by weight of the polyester polyol. In preferred embodiments ofthe invention, the amount of blowing agent in the polyol composition isfrom about 7 to about 30, more preferably from about 20 to about 30,most preferably from about 24 to about 27 parts by weight, based on 100parts by weight of the polyester polyol.

There is also provided a polyisocyanate based rigid closed cell foammade by reacting an organic isocyanate with a polyol composition in thepresence of a blowing agent, wherein the polyol composition comprises:

a) a phthalic anhydride-initiated polyester polyol, preferably having ahydroxyl number of 200 meq. polyolig KOH or more, preferably in anamount of at least 50.0 percent by weight based on the weight of allpolyol components in the polyol composition;

b) a blowing agent; and

c) an oxyethylated fatty acid or fatty alcohol compatibilizing agent.

Again, the blowing agent comprises a C₄-C₆ hydrocarbon and is present inan amount of at least about 5.0 parts by weight, based on 100 parts byweight of the polyester polyol. By employing these constituents in thepolyol composition, the blowing agent is soluble in the polyolcomposition. There is also provided a polyurethane foam comprising thereaction product of an organic isocyanate and a polyol compositioncontaining the aforementioned blowing agent.

There is also provided a method of making a polyisocyanate based rigidclosed cell foam comprising reacting an organic isocyanate with aphthalic anhydride initiated polyester polyol composition into which isincorporated a hydrocarbon blowing agent preferably in an amount of atleast 5.0 parts by weight, based on 100 parts by weight of the polyesterpolyol. Preferably the polyester polyol has a hydroxyl number of 200meq. polyollg KOH or more. In another aspect of the invention, thepolyester polyol is preferably present in the polyol composition in anamount at least 50.0 percent by weight, preferably at least 60.0 percentby weight, most preferably at least 75.0 percent by weight, based on theweight of all polyol components in the polyol composition. Anoxyethylated fatty acid or fatty alcohol compatibilizing agent ispreferably incorporated into the polyol composition.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

There is provided a storage stable polyol composition comprising apolyester polyol, a hydrocarbon blowing agent and a compatibilizingagent. A polyol composition is deemed “storage stable” or “soluble” whenthe polyol composition has the capacity of retaining the blowing agentin solution or in a dissolved state for a period of at least 5 days. Thedetermination of whether or not the blowing agent is in solution ordissolved or soluble is measured by mixing the blowing agent with thepolyol composition ingredients in a clear glass jar, capping the jar,vigorously agitating the contents in the jar and letting the contentsremain still for 5 days at room temperature without agitation. If uponvisual inspection there is no phase separation such that two discretelayers are formed, the blowing agent is deemed soluble in the polyolcomposition, and the polyol composition is deemed storage stable.

This test which lasts at least five days is only for purposes ofmeasuring whether a particular polyol composition formulation isadequate to solubilize the blowing agent. As discussed further below,the blowing agent may be added to the polyol composition weeks prior tofoaming, seconds prior to foaming, or right at the mix head. The scopeof the invention indudes each of these embodiments. By stating that theblowing agent is soluble in the polyol composition, it is meant that thepolyol composition employed must be capable of maintaining a singlephase product by visual inspection. In some cases, this may mean that aparticular blowing agent forms a micro-emulsion with the polyol andother components. An important criteria is the uniform dispersal of theblowing agent during the foaming process as described herein.

Where it is said that the polyol composition “contains” a blowing agentor that the blowing agent is “dissolved in”, “solubilized” or “insolution” with the polyol composition, this would include thoseembodiments where the blowing agent is mixed with the other polyolcomposition ingredients for a period of time sufficient to uniformlydissolve the blowing agent in the polyol composition prior tointroducing the polyol composition into the mix head for reaction withan organic isocyanate compound, and would not include those embodimentswhere blowing agent is metered as a separate stream into a dispensinghead for reaction with an organic isocyanate.

The polyol composition of the present invention contains a phthalicanhydride-initiated polyester polyol, a C₄-C₆ hydrocarbon blowing agentand a oxyethylated fatty acid or fatty alcohol compatibilizing agenthaving an HLB of from about 7 to about 12. Other ingredients that may beincluded in the polyol composition are other polyols, catalysts,surfactants, other blowing agents, flame retardants, fillers,stabilizers and other additives.

The polyester polyols useful in accordance with the teaching of thepresent invention include phthalic anhydride-initiated polyesterpolyols. Preferably, this polyester polyol has a hydroxyl number of atleast 200 meq. polyolig KOH. These polyester polyols provide improveddimensional stability to a rigid foam of the present invention. Thesephthalic anhydride-initiated polyester polyols are generally describedin U.S. Pat. Nos. 4,644,048; 4,644,047; 4,644,027; 4,615,822; 4,608,432;4,595,711; 4,529,744; and 4,521,611, the disclosures of which areincorporated herein by reference.

Particularly preferred polyester polyols of the present inventioninclude STEPANPOL® PS2352, a phthalic anhydride-initiated polyesterpolyol commercially available from Stepan Chemical Company (Northfield,Ill.).

The overall amount of phthalic anhydride-initiated polyester polyol ispreferably at least 50.0 weight percent, more preferably 60.0 weightpercent, most preferably 75.0 weight percent based on the overall weightof all polyol components in the polyol composition. In one embodiment,the phthalic anhydride-initiated polyester polyol is the sole polyolcomponent in the polyol composition. The polyol composition of thepresent invention may contain polyols other than the phthalicanhydride-iniviated polyester polyol described above, e.g., otherpolyester polyols and polyether polyols including aromaticamine-initiated polyols and aliphatic amine-initiated polyols, forexample.

The amount of additional polyols relative to the polyester polyol is notintended to be limited so long as the desired objective of manufacturinga dimensionally stable foam having good thermal insulation values, andoptionally, but preferably solubilizing the blowing agent in the polyolcomposition can be achieved. In this regard, it should be understoodthat the predominant factors in formulating a stable polyol compositionaccording to the present invention include the limited ability of thephthalic anhydride initiated polyester polyol to solubilize blowingagents and the limited ability of specific hydrocarbon blowing agents orblends thereof to blend into polyester polyols, particularly thephthalic anhydride-initiated polyester polyol. At the same time, oneskilled in the art will appreciate that certain hydrocarbon blowingagents will provide distinct physical characteristics to anisocyanate-based foam, which characteristics must be taken into accountwhen developing a polyester polyol composition or rigid foam. Under apreferred embodiment of the present invention the amount of additionalpolyols, including aromatic or aliphatic amine-initiated polyoxyalkylenepolyether polyols and other polyester polyols, present in the polyolcomposition is less than about 20.0, more preferably less than about15.0, most preferably less than about 10.0 percent by weight based onthe weight of all polyol components in the polyol composition.

Suitable additional polyester polyols include those obtained, forexample, from polycarboxylic acids and polyhydric alcohols. A suitablepolycarboxylic acid may be used such as oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid,azelaic acid, sebacic acid, brassylic acid, thapsic acid, maleic acid,fumaric acid, glutaconic acid, a-hydromuconic acid, β-hydromuconic acid,a-butyl-a-ethyl-glutaric acid, a,β-diethylsuccinic acid, isophthalicacid, terephthalic acid, phtalic acid, hemimellitic acid, and1,4-cyclohexanedicarboxylic acid. A suitable polyhydric alcohol may beused such as ethylene glycol, propylene glycol, dipropylene glycol,trimethylene glycol, 1,2 butanediol, 1,5-pentanediol, 1,6-hexanediol,1,7-heptanediol, hydroquinone, resorcinol glycerol, glycerine,1,1,1-trimethylol-propane, 1,1,1-trimethylolethane, pentaerythritol,1,2,6-hexanetriol, a-methyl glucoside, sucrose, and sorbitol. Alsoincluded within the term “polyhydric alcohol” are compounds derived fromphenol such 2,2-bis(4-hydroxyphenol)-propane, commonly known asBisphenol A. Preferred additional polyester polyols are aromaticpolyester polyols.

The hydroxyl-containing polyester may also be a polyester amide such asis obtained by including some amine or amino alcohol in the reactantsfor the preparation of the polyesters. Thus, polyester amides may beobtained by condensing an amino alcohol such as ethanolamine with thepolycarboxylic acids set forth above or they may be made using the samecomponents that make up the hydroxyl-containing polyester with only aportion of the components being a diamine such as ethylene diamine.

Another suitable polyester polyol useful as an additional polyesterpolyol is an alpha-methylglucoside initiated polyester polyol derivedfrom polyethylene terephthalate. This polyol has a molecular weight ofapproximately 358, a hydroxyl number of about 360 meq polyolig KOH and anominal average functionality of 2.3.

As alluded to above, each of the polyols, including the polyesterpolyol, preferably have hydroxyl numbers of 200 or more meq polyoug KOH.At hydroxyl numbers of less than 200, the dimensional stability of thefoam may begin to deteriorate. The optimum nominal functionality ofaromatic polyester polyol appears to be 2 or more, with an averagehydroxyl numbers of 350 or more. Likewise, the optimum nominalfunctionality of each amine-initiated polyol appears to be 4 or more,with hydroxyl numbers of 400 or more.

Other polyols besides the polyester polyols described herein can beadded to the polyol composition provided the desired objectivesdiscussed above can be achieved. Such polyols would includepolyoxyalkylene polyether polyols, polythioether polyols, polyesteramides and polyacetals containing hydroxyl groups, aliphaticpolycarbonates containing hydroxyl groups, amine terminatedpolyoxyalkylene polyethers, polyester polyols, other polyoxyalkylenepolyether polyols, and graft dispersion polyols. In addition, mixturesof at least two of the aforesaid polyols can be used. The preferableadditional polyols are polyoxyalkylene polyether polyols; however, thetotal amount of additional polyols employed will preferably not exceed20.0 weight percent based on the total weight of all polyol componentsin the polyol composition.

Included among polyoxyalkylene polyether polyols are polyoxyethylenepolyols, polyoxypropylene polyols, polyoxybutylene polyols,polytetramethylene polyols, and block copolymers, for examplecombinations of polyoxypropylene and polyoxyethylenepoly-1,2-oxybutylene and polyoxyethylene polyols,poly-1,4-tetramethylene and polyoxyethylene polyols, and copolymerpolyols prepared from blends or sequential addition of two or morealkylene oxides. The polyoxyalkylene polyether polyols may be preparedby any known process such as, for example, the process disclosed byWurtz in 1859 and Encyclopedia of Chemical Technology, Vol. 7, pp.257-262, published by lnterscience Publishers, Inc. (1951) or in U.S.Pat. No. 1,922,459. The alkylene oxides may be added to the initiator,individually, sequentially one after the other to form blocks, or inmixture to form a heteric polyether. The polyoxyalkylene polyetherpolyols may have either primary or secondary hydroxyl groups.

The polyoxyalkylene polyether polyol may have aromatic amine-initiatedor aliphatic amine-initiated polyoxyalkylene polyether polyols. It ispreferred that at least one of the amine-initiated polyols are polyetherpolyols terminated with a secondary hydroxyl group through addition of,for example, propylene oxide as the terminal block. It is preferred thatthe amine-initiated polyols contain 50 weight percent or more, and up to100 weight percent, of secondary hydroxyl group forming alkylene oxides,such as polyoxypropylene groups, based on the weight of all oxyalkylenegroups. This amount can be measured by adding 50 weight percent or moreof the secondary hydroxyl group forming alkylene oxides to the initiatormolecule in the course of manufacturing the polyol.

Suitable initiator molecules for the polyoxyalkylene polyether compoundsare primary or secondary amines. These would include, for the aromaticamine-initiated polyether polyol, the aromatic amines such as aniline,N-alkylphenylene-diamines, 2,4′-, 2,2′-, and 4,4′-methylenedianiline,2,6- or 2,4-toluenediamine, vicinal toluenediamines, o-chloro-aniline,p-aminoaniline, 1,5diaminonaphthalene, methylene dianiline, the variouscondensation products of aniline and formaldehyde, and the isomericdiaminotoluenes, with preference given to vicinal toluenediamines.

For the aliphatic amine-initiated polyol, any aliphatic amine, whetherbranched or unbranched, substituted or unsubstituted, saturated orunsaturated, may be used. These would include, as examples, mono-, di,and trialkanolamines, such as monoethanolamine, methylamine,triisopropanolamine; and polyamines such as ethylene diamine, propylenediamine, diethylenetriamine; or 1,3-diaminopropane, 1,3-diaminobutane,and 1,4-diaminobutane. Preferable aliphatic amines include any of thediamines and triamines, most preferably, the diamines.

Preferably, the additional polyols have number average molecular weightsof 200-750 and nominal functionalities of 3 or more. By a nominalfunctionality, it is meant that the functionality expected is based uponthe functionality of the initiator molecule, rather than the actualfunctionality of the final polyether after manufacture.

The polyoxyalkylene polyether polyols are polyoxyalkylene polyetherpolyols. These polyols may generally be prepared by polymerizingalkylene oxides with polyhydric amines. Any suitable alkylene oxide maybe used such as ethylene oxide, propylene oxide, butylene oxide, amyleneoxide, and mixtures of these oxides. The polyoxyalkylene polyetherpolyols may be prepared from other starting materials such astetrahydrofuran and alkylene oxide-tetrahydrofuran mixtures;epihalohydrins such as epichlorohydrin; as well as aralkylene oxidessuch as styrene oxide.

Other polyoxyalkylene polyether polyols may indude those initiated withpolyhydroxyl compounds. Examples of such initiators aretrimethylolpropane, glycerine, sucrose, sorbitol, propylene glycol,dipropylene glycol, pentaerythritol, and2,2-bis(4-hydroxyphenyl)-propane and blends thereof. The preferredpolyols are initiated with polyhydroxyl compounds having at least 4sites reactive with alkylene oxides, and further may be oxyalkylatedsolely with propylene oxide. In a more preferred embodiment, theadditional polyol is a polyoxyalkylene polyether polyol having a nominalfunctionality of 5 or more, that may be initiated with a polyhydroxylcompound. The high functionality serves to increase the crosslinkdensity to provide a dimensionally stable foam.

Suitable polyhydric polythioethers which may be condensed with alkyleneoxides include the condensation product of thiodiglycol or the reactionproduct of a dicarboxylic acid such as is disclosed above for thepreparation of the hydroxyl-containing polyesters with any othersuitable thioether polyol.

Polyhydroxyl-containing phosphorus compounds which may be used includethose compounds disclosed in U.S. Pat. No. 3,639,542. Preferredpolyhydroxyl-containing phosphorus compounds are prepared from alkyleneoxides and acids of phosphorus having a P₂O₅ equivalency of from about72 percent to about 95 percent.

Suitable polyacetals which may be condensed with alkylene oxides includethe reaction produce of formaldehyde or other suitable aldehyde with adihydric alcohol or an alkylene oxide such as those disclosed above.

Suitable aliphatic thiols which may be condensed with alkylene oxidesinclude alkanethiols containing at least two —SH groups such as1,2-ethanedithiol, 1,2-propanedithiol, 1,2-propanedithiol, and1,6-hexanedithiol; alkene thiols such as 2-butane-1,4-dithiol; andalkene thiols such as 3-hexene-1,6-dithiol.

Also suitable are polymer modified polyols, in particular, the so-calledgraft polyols. Graft polyols are well known to the art and are preparedby the in situ polymerization of one or more vinyl monomers, preferablyacrylonitrile and styrene, in the presence of a polyether polyol,particularly polyols containing a minor amount of natural or inducedunsaturation. Methods of preparing such graft polyols may be found incolumns 1-5 and in the Examples of U.S. Pat. No. 3,652,639; in columns1-6 and the Examples of U.S. Pat. No. 3,823,201; particularly in columns-28 and the Examples of U.S. Pat. No. 4,690,956; and in U.S. Pat. No.4,524,157; all of which patents are herein incorporated by reference.

Non-graft polymer modified polyols are also suitable, for example, asthose prepared by the reaction of a polyisocyanate with an alkanolaminein the presence of a polyether polyol as taught by U.S. Pat. Nos.4,293,470; 4,296,213; and 4,374,209; dispersions of polyisocyanuratescontaining pendant urea groups as taught by U.S. Pat. No. 4,386,167; andpolyisocyanurate dispersions also containing biuret linkages as taughtby U.S. Pat. No. 4,359,541. Other polymer modified polyols may beprepared by the in situ size reduction of polymers until the particlesize is less than 20 mm, preferably less than 10 mm.

The average hydroxyl number of the polyols in the polyol compositionshould preferably be 200 meq polyol/g KOH or more and, more preferably350 meq polyolg KOH or more. Individual polyols may be used which fallbelow the lower limit, but the average should be within this range.Polyol compositions whose polyols are on average within this range makegood dimensionally stable foams.

In addition to the foregoing, the polyester polyol composition of thepresent invention also includes a blowing agent selected from the groupconsisting of C₄-C₆ hydrocarbons and mixtures thereof. The blowing agentmay be added and solubilized in the polyol composition for storage andlater use in a foaming apparatus or may be added to a preblend tank inthe foaming apparatus and preferably solubilized in the polyolcomposition immediately prior to pumping or metering the foamingingredients to the mix head. Alternatively, the blowing agent may beadded to the foaming ingredients in the mix head as a separate stream,although full solubility might be limited due to the short amount oftime the blowing agent is exposed to the polyol composition in the mixhead. The advantage of the polyol composition of the invention is thatthe polyol composition provides the flexibility of storing stable polyolcompositions containing the desired blowing agent, or solubilizing theblowing agent with the polyol composition in the preblend tank, oradding it at the mix head, to manufacture a foam of the desired quality.The polyol composition of the invention is specially adapted to enable avariety of blowing agents to be employed to produce rigid closed cellpolyisocyanate based foams meeting the desired objectives.

The amount of blowing agent used is preferably 5.0 parts by weight ormore based on 100 parts by weight of the polyester polyol in the polyolcomposition. The particular amount of blowing agent will depend in largepart upon the desired density of the foam product. For mostapplications, polyurethane free rise densities for thermal insulationapplications range from free rise densities of 0.5 to 10 pcf, preferablyfrom 1.2 to 2.5 pcf. The preferred overall densities of foams packed to10% by weight, meaning the percentage by weight of foam ingredientsabove the theoretical amount needed to fill the volume of the mold uponfoaming, are from about 1.2 to about 2.5 pcf, more preferably from 1.3to 2.0 pcf. The amount by weight of all blowing agents is generally,based on the weight of the polyol composition, from about 5.0 parts byweight to 40.0 parts by weight, and more preferably, 7.0 parts by weightto 30.0 parts by weight, most preferably from about 20.0 to about 30.0parts by weight, based on 100 parts by weight of the polyester polyol.In one embodiment herein, the blowing agent is present in an amount offrom about 24.0 to about 27.0 parts by weight, based on 100 parts byweight of the polyester polyol.

The blowing agents useful in the polyol composition of the presentinvention are selected from the group consisting C₄-C₆ hydrocarbons andmixtures thereof. The hydrocarbons are preferably the sole blowingagent, optionally with water. Thus, such blowing agents include butanes,pentanes, hexanes, and mixtures thereof. Such blowing agents may belinear, unbranched or cyclic in chemical structure. Preferred blowingagents are the pentanes, i.e., isopentane, normal pentane, cyclopentaneand neopentane. The pentanes may be incorporated into the polyolcomposition of the present invention alone or as a blend of two or morethereof. In one embodiment of the present invention, the blowing agentcomprises a mixture of cyclopentane and isopentane, which preferably hasa weight ratio of between about 70:30 and 40:60. Furthermore, mixturesof normal pentane with isopentane and/or cyclopentane are alsopreferred. Blowing agents comprising isopentane and cyclopentane provideexcellent dimensional stability and insulation properties to a rigidfoam of the present invention. Generally, the selection of the blowingagent utilized will depend on the desired physical characteristics ofthe polyurethane foam. Those skilled in the art are familiar with theeffects provided by the blowing agents of the present invention.

The hydrocarbon blowing agents of the present invention are generallyavailable from manufacturers of fractional distillation products frompetroleum, including Phillips Petroleum and Exxon Corporation. One knownmethod of producing a high purity cyclopentane blowing agent isdisclosed in U.S. Pat. 5,578,652 (Blanpied et al).

The above hydrocarbons may be used as the sole blowing agent in thepresent invention. However, additional limited amounts of auxiliaryblowing agents may be used, including HFC's and HCFC's. Suitablehydrofluorocarbons, perfluorinated hydrocarbons, and fluorinated ethers(collectively referred to herein as HFC's) which are useful asadditional blowing agents include difluoromethane (HFC-32);1,1,1,2-tetrafluoroethane (HFC-134a); 1,1,2,2-tetrafluoroethane(HFC-134); 1,1-difluoroethane (HFC-152a); 1,2-difluoroethane (HFC-142),trifluoromethane; heptafluoropropane; 1,1,1-trifluoroethane;1,1,2-trifluoroethane; 1,1,1,2,2-pentafluoropropane;1,1,1,3,3-pentafluoropropane (HFC 245fa); 1,1,1,3-tetrafluoropropane;1,1,2,3,3-pentafluoropropane; 1,1,1,3,3-pentafluoro-n-butane;1,1,1,2,3,3,3-heptafluoropropane (HFC 227ea); hexafluorocyclopropane(C-216); octafluorocyclobutane (C-318); perfluorotetrahydrofuran;perluoroalkyl tetrahydrofurans; pernluorofuran; perfluoro-propane,-butane, -cyclobutane, -pentane, -cyclopentane, and -hexane,-cyclohexane, -heptane, and -octane; perluorodiethyl ether;perfluorodipropyl ether; and perfluoroethyl propyl ether. Preferredamong the HFC blowing agents are HFC 134a and HFC 236ea, respectively.

Suitable hydrochlorofluorocarbon blowing agents which may also be usedas additional blowing agents are 1-chloro-1,2-difluoroethane;1-chloro-2,2-difluoroethane (142a); 1-chloro-1,1-difluoroethane (142b);1,1-dichloro-1-fluoroethane (141b); 1-chloro-1,1,2-trifluoroethane;1-chloro-1,2,2-trifluoroethane; 1,1-diochloro-1,2-difluoroethane; 1-chloro-1, 1,2,2-tetrafluoroethane (124a);1-chloro-1,2,2,2-tetrafluoroethane (124);1,1-dichloro-1,2,2-trifluoroethane; 1,1-dichloro-2,2,2-trifluoroethane(123); and 1,2-dichloro-1,1,2-trifluoroethane (123a);monochlorodifluoromethane (HCFC-22); 1-chloro-2,2,2-trifluoroethane(HCFC-133a); gem-chlorofluoroethylene (R-1131a);chloroheptafluoropropane (HCFC-217); chlorodifluoroethylene (HCFC-1122);and trans-chlorofluoroethylene (HCFC-1131). Preferred amonghydrochlorofluorocarbon blowing agents is 1,1-dichloro-1-fluoroethane(HCFC-141b).

Other blowing agents which can be used in addition to the blowing agentslisted above may be divided into the chemically active blowing agentswhich chemically react with the isocyanate or with other formulationingredients to release a gas for foaming, and the physically activeblowing agents which are gaseous at the exothermic foaming temperaturesor less without the necessity for chemically reacting with the foamingredients to provide a blowing gas. Included within the meaning ofphysically active blowing agents are those gases which are thermallyunstable and decompose at elevated temperatures.

Examples of chemically active blowing agents are preferentially thosewhich react with the isocyanate to liberate gas, such as CO₂. Suitablechemically active blowing agents include, but are not limited to, water,mono- and polycarboxylic acids having a molecular weight of from 46 to300, salts of these acids, and tertiary alcohols.

Water is preferentially used as a blowing agent. Water reacts with theorganic isocyanate to liberate CO₂ gas which is the actual blowingagent. However, since water consumes isocyanate groups, an equivalentmolar excess of isocyanate must be used to make up for the consumedisocyanates. Water is typically found in minor quantities in the polyolsas a byproduct and may be sufficient to provide the desired blowing froma chemically active substance. Preferably, however, water isadditionally introduced into the polyol composition in amounts of fromabout 0.02 to 5 weight percent, preferably from 0.05 to 4 parts byweight, based on 100 parts by weight of the polyester polyol.

The organic carboxylic acids used are advantageously aliphatic mono- andpolycarboxylic acids, e.g. dicarboxylic acids. However, other organicmono- and polycarboxylic acids are also suitable. The organic carboxylicacids may, if desired, also contain substituents which are inert underthe reaction conditions of the polyisocyanate polyaddifion or arereactive with isocyanate, and/or may contain olefinically unsaturatedgroups. Speciflc examples of chemically inert substituents are halogenatoms, such as fluorine and/or chlorine, and alkyl, e.g. methyl orethyl. The substituted organic carboxylic acids expediently contain atleast one further group which is reactive toward isocyanates, e.g. amercapto group, a primary andlor secondary amino group, or preferably aprimary and/or secondary hydroxyl group.

Suitable carboxylic acids are thus substituted or unsubstitutedmonocarboxylic acids, e.g. formic acid, acetic acid, propionic acid,2-chloropropionic acid, 3-chloropropionic acid, 2,2-dichloropropionicacid, hexanoic acid, 2-ethyl-hexanoic acid, cyclohexanecarboxylic acid,dodecanoic acid, palmitic acid, stearic acid, oleic acid,3-mercapto-propionic acid, glycolic acid, 3-hydroxypropionic acid,lactic acid, ricinoleic acid, 2-aminopropionic acid, benzoic acid,4-methylbenzoic acid, salicylic acid and anthranilic acid, andunsubstituted or substituted polycarboxylic acids, preferablydicarboxylic acids, e.g. oxalic acid, malonic acid, succinic acid,fumaric acid, maleic acid, glutaric acid, adipic acid, sebacic acid,dodecanedoic acid, tartaric acid, phthalic acid, isophthalic acid andcitric acid. Preferable acids are formic acid, propionic acid, aceticacid, and 2-ethylhexanoic acid, particularly formic acid.

The amine salts are usually formed using tertiary amines, e.g.triethylamine, dimethylbenzylamine, diethylbenzylamine,triethylenediamine, or hydrazine. Tertiary amine salts of formic acidmay be employed as chemically active blowing agents which will reactwith the organic isocyanate. The salts may be added as such or formed insitu by reaction between any tertiary amine (catalyst or polyol) andformic acid contained in the polyol composition.

Combinations of any of the aforementioned chemically active blowingagents may be employed, such as formic acid, salts of formic acid,and/or water.

Decomposition type physically active blowing agents that release a gasthrough thermal decomposition include pecan flour, amine/carbon dioxidecomplexes, and alkyl alkanoate compounds especially methyl and ethylformates.

Generally, the blowing agents of the present invention pose particularproblems in incorporation into polyester polyol compositions,particularly phthalic-anhydride-initiated polyester polyols of thepresent invention. It is preferred to have the hydrocarbon blowing agentsolubilized or dissolved in the polyol composition to avoid problems ofseparation of the hydrocarbon and polyol component and accumulation ofthe hydrocarbon blowing agent in the head space. There is particularconcern with the hydrocarbon blowing agents concerning an explosionhazard.

Thus, the polyol composition of the present invention further comprisesan oxyethylated fatty acid or fatty alcohol compatibilizing agent whichhas an HLB of from about 7 to 12 preferably from about 8 to about 11,most preferably from about 8 to about 10.5. This compatibilizing agentfacilitates the incorporation of the hydrocarbon blowing agents into thepolyol composition by solubilizing this blowing agent into the polyolcomposition. The compatibilizing agent appears to reduce the percentageof gas loss during the foaming process when the hydrocarbon blowingagents of the present invention are utilized. Suitable compatibilizingagents include the oxyethylated fatty alcohols having an HLB of fromabout 7 to 12, preferably from about 8 to about 12, most preferably fromabout 8 to about 11.5. Such oxyethylated fatty alcohols preferably havean alkyl chain portion having from about 10 to about 20 carbons. Onesuch oxyethylated fatty alcohol is ICONOL® DAM commercially availablefrom BASF Corporation (Mt. Olive, N.J.), which has an average C₁₀ alkylchain portion, on average four EO units per molecule and has an HLB of10.5. Another such oxyethylated fatty alcohol is ICONOL® TDA-3commercially available from BASF Corporation, which has an average C₁₃alcohol chain portion, an average three EO units per molecule, and hasan HLB of about 8.

Other suitable compatibilizing agents include oxyethlyated fatty acidsof the general formula R_(n)-COO(EO)_(x)H, including mixtures thereof,wherein R_(n) is a branched or unbranched alkyl chain, n being thenumber of carbon atoms in the alkyl chain which is from about 14 toabout 26, EO represents an ethylene oxide unit, and x is from about 5 toabout 12. In a preferred embodiment, on average R_(n) is from about aC₁₆ to about C₂₀ alkyl chain, and x is from about 6 to about 10. Mostpreferably the compatibilizing agent comprises a C₁₈-C₂₀ fattyacid-initiated oxyethylate having an average of about 8 ethylene oxideunits per molecule. Such compatibilizing agents are commerciallyavailable from BASF Corporation (Mt. Olive, N.J.) as INDUSTROL® TFA-8 orMAPEG® 400 MOT. BASF Corporation's MAPEG® 300 MOT is also a suitablecompatibilizing agent.

Other suitable compatibilizing agents include the fatty alcoholethoxylates having a limited portion of propylene oxide incorporatedinto the chemical structure as a heteric portion with the ethylene oxidein the compatibilizing agent structure, such as aC₁₂₋₁₅(EO_(9.7)PO_(3.1)) which is commercially available as PLURAFAC®B25-5 from BASF Corporation. The amount of propylene oxide should belimited to the extent that the above-described HLB values are met, thedesired objective of manufacturing and dimensionally stable foam havinggood thermal insulation values, and optionally, solubilizing the blowingagent in the polyol composition can be achieved.

Although not intending to be bound by theory, it is believed that thepredominant factors in influencing the effectiveness of thecompatibilizing agent to facilitate the incorporation of the blowingagent into the polyester polyol composition include the chain length ofthe alkyl portion of the compatibilizing agent and the HLB of thiscomponent. Generally, longer fatty alkyl chain portions in thecompatibilizing agent provided better capacity to solubilize thehydrocarbon blowing agent into the polyester polyol. The content ofethylene oxide in the chemical structure of the compatibilizing agent isgenerally proportional to its ability to solubilize the hydrocarbonblowing agent.

The amount of a compatibilizing agent required in the polyol compositionof the present invention will depend largely on the components in thepolyol composition particularly the polyester polyol component and theblowing agent utilized. The amount of the compatibilizing agent can beeasily determined by one skilled in the art. Generally, though, acomposition containing cyclopentane as the blowing agent will requireless compatibilizing agent than compositions containing isopentane ornormal pentane. Preferably, the compatibilizing agent is present incompositions containing cyclopentane as the blowing agent in an amountof from about 1 to about 25, more preferably from about 5 to about 15,most preferably from about 7 to about 10 parts by weight, based on 100parts by weight of the polyester polyol in the polyol composition. Incompositions containing isopentane or normal pentane as the blowingagent, the compatibilizing agent is preferably present in amount of fromabout 10 to 25, more preferably from 12 to about 22, most preferablyfrom about 15 to about 20 parts by weight, based on 100 parts by weightof the polyester polyol in the polyol composition. In compositionscontaining 50/50 blends of cyclopentane and isopentane or normal pentaneas the blowing agent, the compatibilizing agent will preferably bepresent in an amount of from about 5 to 20, more preferably from 5 toabout 15, most preferably from about 8 to about 12 parts by weight,based on 100 parts by weight of the polyester polyol in the polyolcomposition.

At all effective levels of compatibilizing agent, preferably containingfrom about 1 to about 25 parts by weight of compatibilizing agent basedon 100 parts by weight of the polyester polyol in the polyolcomposition, compositions of the present invention experience animprovement in the percentage of gas loss during the foaming process ascompared to compositions containing no compatibilizing agent.

Catalysts may be employed which greatly accelerate the reaction of thecompounds containing hydroxyl groups and with the modified or unmodifiedpolyisocyanates. Examples of suitable compounds are cure catalysts whichalso function to shorten tack time, promote green strength, and preventfoam shrinkage. Suitable cure catalysts are organometallic catalysts,preferably organotin catalysts, although it is possible to employ metalssuch as lead, titanium, copper, mercury, cobalt, nickel, iron, vanadium,antimony, and manganese. Suitable organometallic catalysts, exemplifiedhere by fin as the metal, are represented by the formula:R_(n)Sn[X-R¹-Y]₂, wherein R is a C₁-C₈ alkyl or aryl group, R¹ is aC₀-C₁₈ methylene group optionally substituted or branched with a C₁-C₄alkyl group, Y is hydrogen or a hydroxyl group, preferably hydrogen, Xis methylene, an —S—, an —SR²COO—, —SOOC—, an -0₃S—, or an —OOC— groupwherein R² is a C₁-C₄ alkyl, n is 0 or 2, provided that R¹ is C₀ onlywhen X is a methylene group. Specific examples are tin (II) acetate, tin(II) octanoate, tin (II) ethylhexanoate and tin (II) laurate; anddialkyl (1-8C) fin (IV) salts of organic carboxylic acids having 1-32carbon atoms, preferably 1-20 carbon atoms, e.g., diethyltin diacetate,dibutyltin diacetate, dibutyltin diacetate, dibutyltin dilaurate,dibutyltin maleate, dihexyltin diacetate, and dioctywin diacetate. Othersuitable organofin catalysts are organotin alkoxides and mono orpolyalkyl (1-8C) tin (IV) salts of inorganic compounds such as butyltintrichloride, dimethyl- and diethyl- and dibutyl- and dioctyl- anddiphenyl- tin oxide, dibutyltin dibutoxide, di(2-ethylhexyl) tin oxide,dibutyltin dichloride, and dioctyltin dioxide. Preferred, however, aretin catalysts with tin-sulfur bonds which are resistant to hydrolysis,such as dialkyl (1-20C) tin dimercaptides, including dimethyl-,dibutyl-, and dioctyl- tin dimercaptides. A suitable catalyst incompositions of the present invention is K Hex Cem 977 which is apotassium octoate catalyst in a glycol (DPG) carrier commerciallyavailable from M & T Chemicals.

Tertiary amines also promote urethane linkage formation, and includetriethylamine, 3-methoxypropyidimethylamine, triethylenediamine,tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl- andN-cydohexylmorpholine, N,N,N′,N′-tetramethylethylenediamine,N,N,N′,N′-tetramethylbutanediamine or -hexanediamine, N,N,N′-trimethylisopropyl propylenediamine, pentamethyidiethylenetriamine,tetramethyidiaminoethyl ether, bis(dimethylaminopropyl)urea,dimethylpiperazine, 1 -methyl-4-dimethylaminoethylpiperazine,1,2-dimethylimidazole, 1-azabicylo[3.3.0]octane and preferably1,4-diazabicylo[2,2,2]octane, and alkanolamine compounds, such astriethanolamine, triisopropanolamine, N-methyl- andN-ethyidiethanolamine and dimethylethanolamine.

To prepare the polyisocyanurate (PIR) and PUR-PIR foams by the processaccording to the invention, a polyisocyanurate catalyst is employed.Suitable polyisocyanurate catalysts are alkali salts, for example,sodium salts, preferably potassium salts and ammonium salts, of organiccarboxylic acids, expediently having from 1 to 8 carbon atoms,preferably 1 or 2 carbon atoms, for example, the salts of formic acid,acetic acid, propionic add, or octanoic acid, andtris(dialkylaminoethyl)-, tris(dimethylaminopropyl)-,tris(dimethylaminobutyl)- and the correspondingtris(diethylaminoalkyl)-s-hexahydrotriazines. However,(trimethyl-2-hydroxypropyl)ammonium formate,(trimethyl-2-hydroxypropyl)ammonium octanoate, potassium acetate,potassium octoate potassium formate andtris(dimethylaminopropyl)-s-hexahydrotriazine are polyisocyanuratecatalysts which are generally used. The suitable polyisocyanuratecatalyst is usually used in an amount of from 1 to 10 parts by weight,preferably from 1.5 to 8 parts by weight, based on 100 parts by weightof the total amount of polyols.

Urethane-containing foams may be prepared with or without the use ofchain extenders and/or crosslinking agents, which are not necessary inthis invention to achieve the desired mechanical hardness anddimensional stability. The chain extenders and/or crosslinking agentsused have a number average molecular weight of less than 400, preferablyfrom 60 to 300; or if the chain extenders have polyoxyalkylene groups,then having a number average molecular weight of less than 200. Examplesare dialkylene glycols and aliphatic, cycloaliphatic and/or araliphaticdiols having from 2 to 14 carbon atoms, preferably from 4 to 10 carbonatoms, e.g., ethylene glycol, 1,3-propanediol, 1,10-decanediol, o-, m-,and p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, andpreferably 1,4-butanediol, 1,6-hexanediol,bis(2-hydroxyethyl)hydroquinone, triols such as 1,2,4- and1,3,5-trihydroxycyclohexane, glycerol, and trimethylolpropane.

Polyurethane foams can also be prepared by using secondary aromaticdiamines, primary aromatic diamines, 3,3′-di- and/or 3,3′-,5,5′-tetraalkyl-substituted diaminodiphenylmethanes as chain extendersor crosslinking agents instead of or mixed with the abovementioned diolsand/or triols.

The amount of chain extender, crosslinking agent or mixture thereofused, if any, is expediently from 2 to 20 percent by weight, preferablyfrom 1 to 15 percent by weight, based on the weight of the polyolcomposition. However, as previously alluded to, it is preferred that nochain extender/crosslinker is used for the preparation of rigid foamssince the polyether polyols described above are sufficient to providethe desired mechanical properties.

If desired, assistants and/or additives can be incorporated into thereaction mixture for the production of the cellular plastics by thepolyisocyanate polyaddition process. Specific examples includesurfactants, foam stabilizers, cell regulators, fillers, dyes, pigments,flame-proofing agents, hydrolysis-protection agents, and fungistauc andbacteriostatic substances.

Examples of suitable surfactants are compounds which serve to regulatethe cell structure of the plastics by helping to control the cell sizein the foam and reduce the surface tension during foaming via reactionof the polyol composition with an organic isocyanate as describedherein.

Specific examples are salts of sulfonic acids, e.g., alkali metal saltsor ammonium salts of dodecylbenzene- or dinaphthylmethanedisulfonic acidand ricinoleic acid; foam stabilizers, such as siloxane-oxyalkylenecopolymers and other organopolysiloxanes, oxyethylated alkyl-phenols,oxyethylated fatty alcohols, paraffin oils, castor oil esters,ricinoleic acid esters, Turkey red oil and groundnut oil, and cellregulators, such as paraffins, fatty alcohols, anddimethylpolysiloxanes. Preferred surfactants include thesilicone-containing surfactant polymers. The surfactants are usuallyused in amounts of 0.01 to 5 parts by weight, based on 100 parts byweight of the polyol component. A suitable surfactant in compositions ofthe present invention comprises Tegostab® B-8462 silicone surfactantcommercially available from Goldschmidt Company.

For the purposes of the invention, fillers are conventional organic andinorganic fillers and reinforcing agents. Specific examples areinorganic fillers, such as silicate minerals, for example,phyllosilicates such as antigorite, serpentine, homblends, amphiboles,chrysotile, and talc; metal oxides, such as kaolin, aluminum oxides,titanium oxides and iron oxides; metal salts, such as chalk, barite andinorganic pigments, such as cadmium sulfide, zinc sulfide and glass,inter alia; kaolin (china clay), aluminum silicate and coprecipitates ofbarium sulfate and aluminum silicate, and natural and synthetic fibrousminerals, such as wollastonite, metal, and glass fibers of variouslengths. Examples of suitable organic fillers are carbon black,melamine, colophony, cyclopentadienyl resins, cellulose fibers,polyamide fibers, polyacrylonitrile fibers, polyurethane fibers, andpolyester fibers based on aromatic and/or aliphatic dicarboxylic acidesters, and in particular, carbon fibers.

The inorganic and organic fillers may be used individually or asmixtures and may be introduced into the polyol composition or isocyanateside in amounts of from 0.5 to 40 percent by weight, based on the weightof components (the polyol composition and the isocyanate); but thecontent of mats, nonwovens and wovens made from natural and syntheticfibers may reach values of up to 80 percent by weight.

Examples of suitable flameproofing agents are tricresyl phosphate,tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, andtris(2,3dibromopropyl) phosphate. A suitable flame retardant incompositions of the present invention comprises FYROL® PCF, which is atris(chloro propyl)phosphate commercially available from Albright &Wilson.

In addition to the above-mentioned halogen-substituted phosphates, it isalso possible to use inorganic or organic flameproofing agents, such asred phosphorus, aluminum oxide hydrate, antimony trioxide, arsenicoxide, ammonium polyphosphate (Exolit®) and calcium sulfate, expandablegraphite or cyanuric acid derivatives, e.g., melamine, or mixtures oftwo or more flameproofing agents, e.g., ammonium polyphosphates andmelamine, and, if desired, corn starch, or ammonium polyphosphate,melamine, and expandable graphite andlor, if desired, aromaticpolyesters, in order to flameproof the polyisocyanate polyadditionproducts. In general, from 2 to 50 parts by weight, preferably from 5 to25 parts by weight, of said flameproofing agents may be used per 100parts by weight of the polyol composition.

Further details on the other conventional assistants and additivesmentioned above can be obtained from the specialist literature, forexample, from the monograph by J. H. Saunders and K. C. Frisch, HighPolymers, Volume XVI, Polyurethanes, Parts 1 and 2, IntersciencePublishers 1962 and 1964, respectively, or Kunststoff-Handbuch,Polyurethane, Volume VII, Carl-Hanser-Verlag, Munich, Vienna, 1st and2nd Editions, 1966 and 1983; incorporated herein by reference.

Suitable organic polyisocyanates, defined as having 2 or more isocyanatefunctionalities, are conventional aliphatic, cycloaliphatic, araliphaticand preferably aromatic isocyanates. Specific examples include: alkylenediisocyanates with 4 to 12 carbons in the alkylene radical such as1,12-dodecane diisocyanate, 2-ethyl-1,4-tetramethylene diisocyanate,2-methyl-1,5pentamethylene diisocyanate, 1,4-tetramethylene diisocyanateand preferably 1,6-hexamethylene diisocyanate; cycloaliphaticdiisocyanates such as 1,3- and 1,4-cyclohexane diisocyanate as well asany mixtures of these isomers,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate), 2,4- and 2,6-hexahydrotoluene diisocyanate as well as thecorresponding isomeric mixtures, 4,4′- 2,2′-, and2,4′-dicyclohexylmethane diisocyanate as well as the correspondingisomeric mixtures and preferably aromatic diisocyanates andpolyisocyanates such as 2,4- and 2,6-toluene diisocyanate and thecorresponding isomeric mixtures 4,4′-, 2,4′-, and 2,2′-diphenylmethanediisocyanate and the corresponding isomeric mixtures, mixtures of 4,4′-,2,4′-, and 2,2-diphenylmethane diisocyanates andpolyphenylenepolymethylene polyisocyanates (crude MDI), as well asmixtures of crude MDI and toluene diisocyanates. The organic di- andpolyisocyanates can be used individually or in the form of mixtures.Particularly preferred for the production of rigid foams is crude MDIcontaining about 50 to 70 weight percent polyphenyl-polymethylenepolyisocyanate and from 30 to 50 weight percent diphenylmethanediisocyanate, based on the weight of all polyisocyanates used.

Frequently, so-called modified multivalent isocyanates, i.e., productsobtained by the partial chemical reaction of organic diisocyanatesand/or polyisocyanates are used. Examples include diisocyanates and/orpolyisocyanates containing ester groups, urea groups, biuret groups,allophanate groups, carbodiimide groups, isocyanurate groups, and/orurethane groups. Specific examples include organic, preferably aromatic,polyisocyanates containing urethane groups and having an NCO content of33.6 to 15 weight percent, preferably 31 to 21 weight percent, based onthe total weight, e.g., with low molecular weight diols, triols,dialkylene glycols, trialkylene glycols, or polyoxyalkylene glycols witha molecular weight of up to 6000; modwfied 4,4′-diphenylmethanediisocyanate or 2,4- and 2,6-toluene diisocyanate, where examples of di-and polyoxyalkylene glycols that may be used individually or as mixturesinclude diethylene glycol, dipropylene glycol, polyoxyethylene glycol,polyoxypropylene glycol, polyoxyethylene glycol, polyoxypropyleneglycol, and polyoxypropylene polyoxyethylene glycols or -triols.Prepolymers containing NCO groups wih an NCO content of 29 to 3.5 weightpercent, preferably 21 to 14 weight percent, based on the total weightand produced from the polyester polyols and/or preferably polyetherpolyols described below; 4,4′-diphenylmethane diisocyanate, mixtures of2,4′- and 4,4′- diphenylmethane diisocyanate, 2,4,- and/or 2,6toluenediisocyanates or polymeric MDI are also suitable. Furthermore, liquidpolyisocyanates containing carbodiimide groups having an NCO content of33.6 to 15 weight percent, preferably 31 to 21 weight percent, based onthe total weight, have also proven suitable, e.g., based on 4,4′- and2,4′- and/or 2,2′-diphenylmethane diisocyanate and/or 2,4′- and/or2,6toluene diisocyanate. The modified polyisocyanates may optionally bemixed together or mixed with unmodified organic polyisocyanates such as2,4′- and 4,4′-diphenylmethane diisocyanate, polymeric MDI, 2,4′- and/or2,6-toluene diisocyanate.

The organic isocyanates used in the invention preferably have an averagefunctionality of greater than 2, most preferably 2.5 or more. Thisprovides for a greater crosslinking density in the resulting foam, whichimproves the dimensional stability of the foam.

To produce the rigid closed cell polyurethane foams of the presentinvention, the organic polyisocyanate and the isocyanate reactivecompounds are reacted in such amounts that the isocyanate index, definedas the number of equivalents of NCO groups divided by the total numberof isocyanate reactive hydrogen atom equivalents multiplied by 100,ranges from about 80 to less than about 150, preferably from about 90 to110. The polyol composition of the invention provides flexibility in theprocessing window in that the solubility of the polyol composition andthe dimensional stability and thermal insulation of the resulting foamare substantially unaffected throughout a wide range of isocyanateindices. If the rigid foams contain, at least in part, bondedisocyanurate groups, an isocyanate index of 150 to 6000, preferably from200 to 800, is usually used.

In a method of the invention, there is provided the reaction of anorganic isocyanate with a polyester polyol composition wherein thepolyol composition comprises:

a) a phthalic anhydride polyester polyol preferably having a hydroxylnumber of 200 meq. polyol/g KOH or more.

b) a blowing agent selected from the group consisting C₄-C₆ hydrocarbonsand mixtures thereof; and

c) an oxyethylated fatty acid or fatty alcohol compatibilizing agenthaving an HLB of from about 7 to about 12.

Optionally, but preferably, the hydrocarbon based blowing agent isdissolved in the polyol composition. In one embodiment, the polyolcomposition contains the blowing agent in solution prior to reactionwith the organic isocyanate. Preferably, the organic isocyanate and thepolyol composition are reacted at isocyanate indices ranging from 80 to350. All throughout this range the K-factors of the foam aresubstantially constant and the foams are dimensionally stable. Asubstantially constant K-factor value means that the variance in valuesis ±10 percent or less between the lowest and highest values within therange. Throughout the range, the foam also remains dimensionally stableas defined below. The measurements for the K-factor are taken from coresamples as described below in the definition of a dimensionally stablefoam and are the initial K-factors.

The rigid foams made from polyisocyanate polyaddition products areadvantageously produced by the one-shot process, for example, usingreaction injection moldings, or the high pressure or low pressuremethod, in an open or closed mold, for example, in a metallic mold, orin a pour-in-place application where the surfaces contacting thereaction mixture become a part of the finished article. In a preferredembodiment, rigid foams may be made in a continuous laminate process,which process is well know in the industry.

The starting components may be mixed at from 15° C. to 90° C.,preferably from 20° C. to 35° C., and introduced into the open or closedmold, if desired under super-atmospheric pressure. The mixing of theisocyanate with the polyol composition containing dissolved blowingagent can be carried out mechanically by means of a stirrer or astirring screw or under high pressure by the impingement injectionmethod. The mold temperature is expediently from 20° C. to 110° C.,preferably from 30° C. to 60° C., in particular from 45° C. to 50° C.

The rigid foams produced by the process according to the invention andthe corresponding structural foams are used, for example, in the vehicleindustry—the automotive, aircraft, and ship building industries—and inthe furniture and sports goods industries. They are particularlysuitable in the construction and refrigeration sectors as thermalinsulators, for example, as intermediate layers for laminate board orfor foam-filling refrigerators, freezer housings, and picnic coolers.

For pour-in-place applications, the rigid foam may be poured or injectedto form a sandwich structure of a first substrate/foam/second substrateor may be laminated over a substrate to form a substrate foam structure.The first and second substrate may each be independently made of thesame material or of different materials, depending upon the end use.Suitable substrate materials comprise metal such as aluminum, tin, orformed sheet metal such as used in the case of refrigeration cabinets;wood, including composite wood; acrylonirile-butadiene-styrene (ABS)triblock of rubber, optionally modified with styrene-butadiene diblock,styrene-ethylene/butylene-styrene triblock, optionally functionalizedwith maleic anhydride and/or maleic acid, polyethylene terephthalate,polycarbonate, polyacetals, rubber modified high impact polystyrene(HIPS), blends of HIPS with polyphenylene oxide, copolymers of ethyleneand vinyl acetate, ethylene and acrylic acid, ethylene and vinylalcohol, homopolymers or copolymers of ethylene and propylene such aspolypropylene, high density polyethylene, high molecular weight highdensity polyethylene, polyvinyl chloride, nylon 66, or amorphousthermoplastic polyesters. Preferred are aluminum, tin, ABS, HIPS,polyethylene, and high density polyethylene.

The polyurethane foam may be contiguous to and bonded to the innersurfaces of the first and second substrates, or the polyurethane foammay be contiguous to a layer or lamina of synthetic material interposedbetween the substrates. Thus, the sequence of layers in the compositemay also comprise a first substrate/polyurethane foam/layer orlamina/second substrate or first substrate/layer or lamina/polyurethanefoam/layer or lamina/second substrate.

The layer or lamina of layers additionally interposed into the compositemay comprise any one of the above-mentioned synthetic resins which havegood elongation such as low density polyethylene or low density linearpolyethylene as a stress relief layer or a material which promotesadhesion between the polyurethane foam and the first and/or secondsubstrate of choice.

When a synthetic plastic material such as polyethylene having few or nobonding or adhesion sites is chosen as the first and/or second substrateas an alternative to an adhesion-promoting layer, it is useful to firstmodify the substrate surface with a corona discharge or with a flametreatment to improve adhesion to the polyurethane foam.

During the foam-in-place operation, the substrates are fixed apart in aspaced relationship to define a cavity between the first substrate andsecond substrate, and optionally the inner surface of at least onesubstrate, preferably both, treated to promote adhesion. This cavity isthen filled with a liquid polyurethane system which reacts and foams insitu, bonding to the inner surfaces of the first and second substrates.In the case of a refrigeration unit or a cooler container, such as apicnic cooler, a thermoformed inner liner material is inserted into theouter shell of cooler or the refrigeration cabinet, in a nested spacedrelationship to define a cavity, which cavity is then filled with afoamed-in-place polyurethane foam. In many cases, it is only thepolyurethane foam which holds together the outer shell and inner liner,underscoring the need for foam dimensional stability.

The polyurethane cellular products of the invention are rigid, meaningthat the ratio of tensile strength to compressive strength is high, onthe order of 0.5:1 or greater, and having less than 10 percentelongation. The foams are also closed cell, meaning that the number ofopen cells is 20% or less, or conversely the number of closed cells is80% or greater, the measurement being taken on a molded foam packed at10% over the theoretical amount required to fill the mold with foam.

The rigid polyurethane cellular products of the invention aredimensionally stable, exhibiting little or no shrinkage, even at freerise densities of 2.0 pcf or less. In a preferred embodiment, the rigidpolyurethane cellular products of the invention tested according to ASTMD 2126-87 using core samples of density 2.0 pcf or less with dimensionsof 3″×3″×1″ and taken from a 10% packed boxes measuring 4″×10″×10″advantageously have the following dimensional changes at 28 days ofexposure: at 100 F/100 percent RH, i.e., relative humidity, no more than±5 percent, more preferably no more than ±3 percent; at 158 F/100percent RH no more than ±5 percent, most preferably less than ±4percent; at 158 F, dry no more than ±8 percent, preferably no more than±6 percent; at 200 F, dry no more than ±5, preferably no more than ±3percent; and at −20 F after 7 days exposure no more than ±5 percent,preferably no more than ±3 percent.

The thermal insulation values of the rigid closed cell foams accordingto the preferred embodiments of the invention are 0.160BTU-in./hr.-ft²-F or less initial, more preferably 0.150 or lessinitial, measured from the core of a 10% overpacked sample. It has beenfound that foams made with the phthalic-anhydride-initiated polyesterpolyols exhibit relatively low k-factors.

In a preferred embodiment, the rigid polyurethane foams are alsoadvantageously not friable at their surface in spite of their lowdensity and the presence of polyols having a high hydroxyl number andlow equivalent weight. These foams typically exhibit a surfacefriability of less than 5 percent when tested according to ASTM C 421,at core densities of 2.0 pcf or less, even at core densities of 1.5 pcfor less. The low surface friability enables the foam to adhere well tosubstrates.

The term polyisocyanate based foam as used herein is meant to includepolyurethane-polyurea, polyurethane-polyisocyanurate, polyurethane, andpolyisocyanurate foams.

The following examples illustrate the nature of the invention withregard to the formation of stable polyester polyol compositions and theresulting isocyanate-based rigid foam prepared therefrom. The examplespresented herein are intended to demonstrate the objects of theinvention but should not be considered as limitations thereto. Unlessotherwise indicated, all parts are expressed in parts by weight.

EXAMPLES

Isocyanate A is a polymethylene polyphenylene polyisocyanate having afree NCO content of about 31 percent, a nominal functionality of about 3and a viscosity of 700 cP at 25° C.

Polyester Polyol is a phthalic anhydride-initiated polyester polyolhaving a nominal functionality of about 2 and hydroxyl number of about240.

Flame Retardant is a tris(chloro propyl)phosphate.

Surfactant is a silicone surfactant polymer.

Catalyst is a potassium octoate catalyst in a dipropylene glycolcarrier.

Compatibilizer is a long chain fatty acid initiated oxyethylate havingon average about 8 ethylene oxide units per molecule and an HLB of about10.

Commercial cyclopentane is a product containing between about 80 and 85%cyclopentane isomer which is commercially available from Phillips 66Company.

Pure cyclopentane is a high purity reagant grade cyclopentane productcommercially available from Exxon Corporation containing greater thanabout 90% cyclopentane isomer.

Procedure for Resin Blend: The amount of polyester polyol is weighed andplaced into a glass bottle. The desired quantity of surfactant,catalyst, compatiblizer and flame retardant are added into the glassbottle container. Generally, the components may be added in any order.The desired amount of hydrocarbon blowing agent is dispensed into theglass container. The contents are sealed by tightening the cap on thebottle. The contents are then mixed by vigorously shaking the bottle.The contents are allowed to remain at rest for 5 days at roomtemperature without agitation. If upon visual inspection there is nophase separation (clear resin blend) such that two discrete layers areformed, the blowing agent is deemed soluble in the polyol composition,and the polyol composition is deemed storage stable.

Procedure for production of Polyurethane Foam: The polyol composition isthen reacted with an amount of Isocyanate A at a foam index ratio of 300such that the calculated ratio of NCO groups in the isocyanate is threetimes the number of hydroxyl groups in the resin components. Theisocyanate is mixed and reacted with the resin blend at about roomtemperature using a high speed propeller mixer. Gas loss for thesehandmixes is determined according to the following procedure.

Procedure for gas loss determination: Supplies required: polypropylenetubs (approximately 8″ in diameter and 10″ in height) with ½″ draintubes located about ½ below the open rim of the tub; laboratory balance;barometer; thermometer; water; and foam mixing equipment (high speedpropeller mixer). Place a polypropylene tub on the laboratory balanceand tare the balance. Fill the polypropylene tub with water above thedrain tube and allow it to drain until draining stops. Record the waterweight needed to fill the tub. Record the water temperature. Repeat atleast ten times and calculate the average water weight needed to fillthe tub. Empty the water from the tub and dry it out. Coat the inside ofthe tub with a release agent, such as paste wax to ease removal of foam.Place the tub on the balance and tare the balance. Mix a foam handmixusing normal laboratory technique. Pour approximately 200 grams of mixedfoam into a polypropylene tub and immediately record the weight of thefoam before it starts to rise. Note: Exact weights are not critical inthis operation, speed is. Dump the foam quickly into the tub and readthe weight of the liquid on the balance as quickly as possible. Allowthe foam to rise in the tub. Note: The foam should not rise above thelevel of the drain tube. After several minutes, the foam weight willstabilize. Record this value. Tare the balance to zero Fill the tub withwater above the drain tube and allow it to drain until it stops. Recordthe weight of the water in the tub. Record the water temperature. Removefoam from the tub. Measure and record the barometric pressure, theambient air temperature and the wet bulb

TABLE 1 SAMPLE Component 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17Polyester Polyol 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Flame Retardant 10.010.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.010.0 10.0 Surfactant 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.02.0 2.0 2.0 2.0 Catalyst 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.52.5 2.5 2.5 2.5 2.5 Compatibilizer 0.0 5.0 0.0 5.0 0.0 5.0 10.0 15.020.0 0.0 5.0 10.0 15.0 20.0 0.0 5.0 10.0 COMMERCIAL 25.0 25.0 — — — — —— — — — — — — — — — CYCLOPENTANE PURE — — 25.0 25.0 — — — — — — — — — —— — — CYCLOPENTANE ISOPENTANE (IP) — — — — 25.0 25.0 25.0 25.0 25.0 — —— — — — — — NORMAL PENTANE — — — — — — — — — 25.0 25.0 25.0 25.0 25.0 —— — (NP) CP/IP BLEND 50/50 — — — — — — — — — — — — — — 25.0 25.0 25.0CP/NP BLEND 50/50 — — — — — — — — — — — — — — — — — TOTAL: 139.5 144.5139.5 144.5 139.5 144.5 149.5 154.5 159.5 139.5 144.5 149.5 154.5 159.5139.5 144.5 149.5 CLEAR RESIN BLEND YES YES YES YES NO NO NO NO YES NONO NO NO YES NO NO YES Component 18 19 20 Polyester Polyol 100.0 100.0100.0 Flame Retardant 10.0 10.0 10.0 Surfactant 2.0 2.0 2.0 Catalyst 2.52.5 2.5 Compatibilizer 0.0 0.5 10.0 COMMERCIAL — — — CYCLOPENTANE PURE —— — CYCLOPENTANE ISOPENTANE (IP) — — — NORMAL PENTANE — — — (NP) CP/IPBLEND 50/50 — — — CP/NP BLEND 50/50 25.0 25.0 25.0 TOTAL: 139.5 144.5149.5 CLEAR RESIN BLEND NO NO YES Blowing Agent Loss = Wt._(liquid foam)− Wt._(cured foam) − Density_(ambient air) [(Wt._(total water) −Wt._(partial water))/(Density_(water) × 1000)] where:Density_(ambient air) = (MW_(ambient air) × Bar. Press.)/1.362833(Temp._(dry bulb) + 460) MW_(ambient air) = (28.964 × Dry MoleFraction) + (0.18 × Absolute Moisture_(ambient air)) Dry Mole Fraction =1 − (Absolute Moisture_(ambient air)/100) AbsoluteMoisture_(ambient air) = [Vap. Press._(water @ wet bulb temp.) − (3.67 ×10⁻²)(Bar. Press.)(Temp._(dry bulb) − Temp._(wet bulb))[1 +(Temp._(wet bulb) − 32)1571]]/Bar. Press.

temperature. Calculate the gas loss for each foam using the equationsappearing below Table 1.

Results: Samples 2; and 4; and 6-9; and 11-14; and 16-17; and 19-20exhibit an improvement in percentage of gas loss during the process ofproducing a polyurethane foam over Samples 1; and 3; and 5; and 10; and15; and 18, respectively. Further, Table 1 demonstrates the approximatelevel of compatibilizing agent required for the compositions displayedusing different blowing agents to provide a storage stable polyesterpolyol composition in accordance with the present invention.

What is claimed is:
 1. An isocyanate-based rigid foamn comprising thereaction product of: a) an organic and/or modified organicpolyisocyanate and b) a polyol composition wherein said polyolcomposition comprises at least 75% by weight of a phthalicanhydride-initiated polyester polyol, a compatibilizing agent having anHLB of from about 7 to about 12 and selected from the goup consisting offatty alcohol ethyoxylates having a general formula ofC_(n)(EO)_(x)(PO)_(y), wherein n is from 10 to 20, EO representsethylene oxide uits and x is from 3 to 10, and PO represents propyleneoxide units and y is from 0 to 3, and oxyethylated fatty acids having ageneral formula of R_(n)COO(EO)_(x)H, wherein R_(n) is a C₁₄ to a C₂₆alkyl chain, EO represents ethylene oxide units and x is from 5 to 12,and a blowing agent selected from the group consisting of C₄-C₆hydrocarbons and mixtures thereof, and, optionally, a relatively lowmolecular weight chain extender or crosslinker, a surfactant, a catalystand further auxiliaries and/or additives, wherein said blowing agent issoluble in the polyol composition for at least 5 days.
 2. A rigid foamas defined in claim 1, wherein the compatibilizing agent comprises aC₁₈-C₂₀ fatty acid initiated oxyethylate having an average of about 8ethylene oxide units per molecule.
 3. A rigid foam as defined in claim1, wherein the compatibilizing agent is present in an amount of fromabout 1.0 to about 25.0 parts by weight based on 100 parts by weight ofthe polyester polyol.
 4. A rigid foam as defined in claim 1, wherein thecompatibilizing agent is present in an amount of from about 5.0 to about15.0 parts by weight based on 100 parts by weight of the polyesterpolyol.
 5. A rigid foam as defined in claim 2, wherein thecompatibilizing agent is present in an of from about 5.0 to about 15.0parts by weight based on 100 parts by weight of the polyester polyol. 6.A rigid foam as defined in claim 1, wherein the amount of blowing agentis at least 5.0 parts by weight based on 100 parts by weight of thepolyester polyol.
 7. A rigid foam as defined in claim 1, wherein saidblowing agent is selected from the group consisting of isopentane,normal pentane, neopentane, cyclopentane and mixtures thereof.
 8. Arigid foam as defined in claim 1 wherein the blowing agent furthercomprises water in an amount of from about 0.05 to 4 parts by weightbased on 100 parts by weight of the polyester polyol.
 9. A rigid foam asdefined in claim 1 wherein the polyol composition further comprisesaromatic or aliphatic amine initiated polyoxyalkylene polyether polyolsor polyester polyols other than the phthalic anhydride initiatedpolyester polyol in an amount of less than 20.0 weight percent based onthe weight of all polyol components in the polyol composition.
 10. Arigid foam as defined in claim 1 wherein the polyol composition furthercomprises assistants and/or additives.
 11. An isocyanate-based foamcomprising the reaction product of: a) an organic and/or modifiedorganic polyisocyanate with b) a polyol composition wherein said polyolcomposition comprises at least 75% by weight of a phthalicanhydride-initiated polyester polyol, a compatibilizing agent having anHLB of from about 7 to about 12 and selected from the goup consisting offatty alcohol ethyoxylates having a general formula ofC_(n)(EO)_(x)(PO)_(y), wherein n is from 10 to 20, EO representsethylene oxide units and x is from 3 to 10, and PO represents propyleneoxide units and y is from 0 to 3, and oxyethylated fatty acids having ageneral formula of R_(n)COO(EO)_(x)H, wherein R_(n) is a C₁₄ to a C₂₆alkyl chain, EO represents ethylene oxide units and x i s from 5 to 12,and a blowing agent comprising a C₅ hydrocarbon, and, optionally, arelatively low molecular weight chain extender or crosslinker, asurfactant, a catalyst and further auxiliaries and/or additives, whereinsaid blowing agent is soluble in the polyol composition for at least 5days.
 12. A rigid foam as defined in claim 11, wherein thecompatibilizing agent comprises a C₁₈-C₂₀ fatty acid initiatedoxyethylate having an average of about 8 ethylene oxide units permolecule.
 13. A rigid foam as defined in claim 11, wherein thecompatibilizing agent is present in an amount of from about 1.0 to about25.0 parts by weight based on 100 parts by weight of the polyesterpolyol.
 14. A rigid foam as defined in claim 11, wherein thecompatibilizing agent is present in an amount of from about 5.0 to about15.0 parts by weight based on 100 parts by weight of the polyesterpolyol.
 15. A rigid foam as defined in claim 11, wherein thecompatibilizing agent is present in an amount of from about 5.0 to about15.0 parts by weight based on 100 parts by weight of the polyesterpolyol.
 16. A rigid foam as defined in claim 11, wherein the blowingagent comprises a mixture of isopentane and/or normal pentane andcyclopentane.
 17. A rigid foam as defined in claim 11, wherein theamount of blowing agent is at least 5.0 parts by weight based on 100parts by weight of the polyester polyol.
 18. A rigid foam as defined inclaim 11 further comprising water in an amount of from about 0.05 to 4parts by weight based on 100 parts by weight of the polyester polyol.19. An isocyanate-based rigid foam comprising the reaction product of:a) an organic and/or modified organic polyisocyanate with b) a polyolcomposition wherein said polyol composition comprises at least 75% byweight of a phtalic anhydride-initiated polyester polyol, acompatibilizing agent comprising a C₁₈-C₂₀ fatty acid-initiatedoxyethylate having an average of about 8 ethylene oxide units permolecule and having an HLB of about 10, and a blowing agent comprisingisopentane and cyclopentane in a weight ratio of from about 30:70 toabout 40:60, and, optionally, a relatively low molecular weight chainextender or crosslinker, a surfactant, a catalyst and furtherauxiliaries and/or additives, wherein said blowing agent is soluble inthe polyol composition for at least five days.